The present disclosure relates to three-dimensional imaging and modeling of physical objects. In particular, the present disclosure relates to texture mapping three-dimensional models of physical objects. In some instances, the present disclosure relates to texture mapping of three-dimensional models representing one or more dental articles, such as molds, castings, dentition, prepared dentition, soft tissue (e.g., gums), and/or other dental articles.
Techniques have been developed to generate three-dimensional (“3D”) models of physical objects. The 3D models are generated by a computer that processes data representing the surfaces and contours of the physical object. The data is generated by optically scanning the physical object and detecting or capturing the light reflected off of the object. Based on various processing techniques such as Moire, interferometry, triangulation, or otherwise the shape, surfaces, and/or contours of the object are modeled by the computer.
In some instances, a 3D digitizer is used to produce a 3D model of the physical object by observing the object from a number of different positions. Each position produces a cloud of 3D coordinates. The complete 3D model is generated from a superposition of the multiple 3D point clouds. A 3D model built in this manner contains only the coordinate information, and has no texture associated with it since the underlying data is in the form of collections of 3D coordinates only. In some instances an image of the object is taken from each different position. Each image is represented by a collection of pixels, usually arranged in a rectangular array. By correlating the pixels of the images to the 3D coordinates of the model, the images can be projected or mapped onto the 3D model to provide texture to the 3D model. The methods employed for such mappings perform an offline computation where all of the textures are merged or blended together onto the model. These methods—which are computationally expensive and slow—typically cannot be employed in real time 3D modeling situations where new images are being added to a 3D model as the 3D is built and the user expects to see the results immediately. Also, the merging and blending of the textures are designed to improve the appearance of the 3D model, which can result in an inaccurate depiction of the texture in the 3D model as compared to the actual physical object.
There are also a number of complications that arise when texture mapping a 3D model with several images or views. First, in some instances the images will overlap, in which case a choice must be made as to which part of which image should be mapped to a particular part of the 3D model. In addition, if a light source is attached to the digitizer, then in every image the lighting conditions are different, which can cause the same area of the object to have a different appearance or texture in the different images. Further, while illuminating the object from a single fixed point relative to the object may limit some of the effects of having different lighting conditions for the different positions, the resulting images may have shadows that detract from the realism of the model. Further still, in the context of dental imaging some imaging devices require powdering or coating of the treatment site with a contrast or reflective material, such as titanium dioxide, in order to obtain the reflections utilized in determining the 3D coordinates. The powdering or coating of the treatment site prevents acquisition of the actual texture and color of the treatment site during the 3D data acquisition, in addition to increasing or introducing errors in the 3D coordinate data caused by non-uniformity of the powder thickness.
Accordingly, there is a need for improved methods, systems, and devices for three-dimensional modeling of physical objects and, in particular, texture mapping three-dimensional models of dental articles.